Many studies on an artificial liver and the like have been conducted. However, cell culture of only a hepatic parenchymal cell for a long period of time has not been realized. The present inventors have reported that high liver functions are expressed by using a co-culture system of an endothelial cell and a hepatic parenchymal cell which forms a structured network due to the selection of a scaffold material, in the short term (see Non-Patent Document 1). A structure of a device suited for this system is disclosed, for example, in Patent Document 1.